The Collaborative International Dictionary of English v.0.48:

Oxyhydrogen \Ox`y*hy"dro*gen\, a. [Oxy
   (a) + hydrogen.] (Chem.) Of, pertaining to, or consisting of,
       a mixture of oxygen and hydrogen at over 5000[deg] F.
       [Webster 1913 Suppl.]

   Oxyhydrogen blowpipe. (Chem.) See Blowpipe.

   Oxyhydrogen microscope, a form of microscope arranged so as
      to use the light produced by burning lime or limestone
      under a current of oxyhydrogen gas.
      [1913 Webster]